Flame sensitive ignitor

ABSTRACT

A flame-sensitive ignitor for an explosive charge, comprising a capsule containing a primer charge sensitive to flame ignition and a foil cover for retaining the charge within the capsule, wherein a recess is formed between the foil cover and the surface of the primer charge.

United States Patent Prior Sept. 12, 1972 [54] FLAME SENSITIVE IGNITOR [72] V Inventor: Josef Prior, Victoriastr. 11,

Troisdorf, Germany [22] Filed: July 3, 1969 [21] Appl. No.: 838,919

[52] US. Cl ..102/86.5, 102/27 R, 102/70 [51] Int. Cl. ..F42c 19/08 [58] Field of Search ..l02/27, 70, 86.5

[56] References Cited UNITED STATES PATEN'IS 2,441,248 5/1948 Morris et al. "10 2/27 X Gey ..102/86.5 Bjorklund et al. l02/86.5

Primary Examiner-Verlin R. Pendegrass Att0rney-Craig and Antonelli [5 7] ABSTRACT 10 Claims, 4 Drawing Figures P'A'IENTEDsEP 12 m2 3.690.260

INVENTOR JOSEF PRIOR ATTORNEYS BACKGROUND OF THE INVENTION Conventional primers, such as detonators and delay fuse components which are sensitive to flame ignition, are provided with combustible charges of substances such as pyrotechnical compositions, gun powder, or trizinate-containing mixtures. These flame-sensitive charges are generally covered by a foil or the like in order to effectively prevent leakage of the charge from the container since the primers may be subjected to considerable vibration and impact stresses during transportation. The use of a foil cover, however, in-

volves considerable difficulty in attaining the desired reliability inasmuch as the foil cover may prevent ignition of the primer in the presence of an ignition flame of relatively low intensity, which flame may be unable to penetrate the foil cover.

These problems have been overcome, to some extent, by constructing the foil from a nitrocellulose material which is itself readily flammable. This material, however, has been found to be extremely difficult to work with insofar as it is desired to produce covers of a particular shape and exhibiting a sufficient elasticity.

As noted above, however, when the foil cover is fabricated from other materials which are less highly flammable, even though the cover is made extremely thin, it has been found that considerable impact energies are required in order to rupture the cover to facilitate flame ignition. Since the energy required for the initiation of flame ignition under these circumstances may not be available, the reliability of the primers is considerably lower than desired.

Accordingly, it is an objective of the present invention to provide an ignitor sensitive to flame ignition with a cover affording the desired protection against leakage of the primer charge without seriously impairing'the reliability of the primer even in the presence of a relatively low-intensity ignition flame.

Further, it is an objective of the present invention to provide an ignitor with a cover fabricated from a material other than nitrocellulose which nevertheless insures flame ignition in the presence of a relativelylow intensity flame.

Finally, it is an objective of the present invention to provide a reliable ignitor, sensitive to flame ignition which exhibits greater reliability than conventional devices of this type and which is relatively simple and inexpensive to produce.

SUMMARY OF THE INVENTION The aforementioned objectives are accomplished, in accordance with the present invention, by the formation of a recess or cavity between the foil cover and the surface of the primer charge within the container. The foil cover, which may be fabricated from any desired material, but preferably aluminum, is therefore not in contact with the primer charge, but rather spaced therefrom by the cavity formed within the charge. lgnitors constructed in this manner have been found to be sensitive, even in the presence of minor shock impulses, to the extent that the foil is ruptured in the direction of the cavity formed within the primer charge and, accordingly, the ignition of the primer charge is initiated.

The recess or cavity mentioned above can be produced simply by making a depression, for example, in the form of a spherical impression, by means of a forming die, within the mass of the primer charge. Thereafter, the surface of the primer charge having the cavity-formed therein is covered with a foil cover, thereby effectively sealing off the primer charge from leaking out of the container provided therefor in the presence of vibrational forces or other shocks and also protecting the primer charge from the effects of possibly damaging external influences such as moisture.

An additional advantage is inherent in the use of a forming die to form a cavity within the primer charge in that the surface of the charge is so compressed that greater security against crumbling of the primer charge results. The inventive concept of the present invention may additionally or alternatively be carried out by forming the recess or cavity simply by attaching the foil cover at a point spaced from the surface of the primer composition, for example, such that the rim of a capsule or cartridge containing the primer charge extends beyond the surface of the primer charge and is covered at its end by means of a foil cover.

BRIEF DESCRIPTION OF THE DRAWINGS The aforementioned objectives, features and advantages of the present invention will become more readily apparent from a consideration of the detailed description hereinbelow, when considered in conjunction with the accompanying drawings, wherein:

FIG. 1 represents a sectional view of an ignitor constructed in accordance with the present invention;

FIG. 2 represents an ignitor according to the present invention inserted within a member adapted to receive same;

FIG. 3 represents an ignitor accommodated within a capsule having an external thread; and

FIG.- 4 represents a further embodiment of an ignitor according to the present invention, having an external thread.

DETAILED DESCRIPTION OF THE DRAWINGS As seen in FIG. 1, a container or capsule 1 contains the explosive charge actually composed of discrete zones of explosives of different types, including a flamesensitive primer charge 3, the initiating charge 4 and the sustaining charge 5. The capsule or container 1 is effectively closed, at the lower end thereof, by means of a cover or end plate 6 retained by means of the flanged portion of the projecting end of the container. At the opposite or upper end of the container or capsule l, a central ignition bore or flash vent 8 is provided. By impressing a forming die (not shown) through the ignition bore 8 into the primer charge 3, a cavity 7 is produced.

It should be readily apparent that the surface of the primer charge 3 is considerably reinforced in the region of the cavity 7 by the compressive force of the forming die, thereby rendering the primer charge 3 far less likely to crumble.

The foil cover 2, fabricated, for example, from aluminum, is secured to the open end of the capsule l, by means of gluing, cementing or the like, so that the capsule is securely sealed. During ignition of the ignitor device by means of a flameapplied thereto, even minor shock impulses are sufficient for penetrating the foil cover 2 in the direction of the cavity 7 to ignite the primer charge 3.

The capsule or container 1, as illustrated in FIG. 2, is inserted within a receiving member 9, for example, the rotor of a projectile ignitor such that the cavity 11 is produced between the front end 10 of the receiving member 9 and the ignition bore 8 of the ignitor. The cavity 11 is closed off by means of the foil cover 2 which is attached or glued to the front end of the receiving member 9; a cap 12 with a central aperture 15 therein is disposed above the foil cover 2. Otherwise, the ignitor is constructed in the same manner as that illustrated in FIG. 1.

In the embodiment illustrated in FIG. 3, the charge 5, the initiator charge 4 and the flame-sensitive primer charge 3 are inserted in the cup-shaped container 1 which is provided with an external thread 13. The primer charge 3 is covered by the inner cap 14 which is provided with a flash vent 8. Between the inner cap 14 and the front end 10 of the container 1, a free space 1 l is provided. The container 1 is sealed at its open end by means of the cap 12, the central portion 16 of which is reduced in its wall thickness to such an extent that it is comparable to the foil cover 2 of the embodiments illustrated in FIGS. 1 and 2.

The ignitors illustrated in FIGS. l-3 include a cavity 7 formed within the primer charge 3, to which additional space may be added selectively in accordance with the free space 11 illustrated in FIGS. 2 and 3.

However, the present invention is not restricted to these embodiments; rather, the invention also contemplates, for example, an arrangement such as that illustrated in FIG. 4. In this instance, the initiator charge 4 and the flame-sensitive charge 3 are successively introduced and tamped down into the capsule or container 1, which capsule is closed at one end and provided with an external thread 13. A cavity 11 is provided between the surface of the primer charge 3 and the open front end of the capsule l. The capsule 1 is then covered by means of cap 12, the central part 16 of which is, like that illustrated in FIG. 3, provided with a substantially reduced wall thickness, so that even a relatively minor shock impulse of low intensity is sufficient for penetrating the cap in the zone 16 of reduced thickness, in the presence of a flame ignition, and to initiate the ignition of the primer charge 3. Of course, it is also possible to fabricate the cover of the capsule 1 in accordance with that illustrated in the embodiment of FIG. 2.

While the present invention has been described with reference to the specific details of four embodiments, it is to be understood that the scope of the invention is not limited to the specific details of these embodiments, but is susceptible of numerous changes and modifications as would be apparent to one with normal skill in the pertinent technology.

What is claimed is:

l. A flame-sensitive ignitor for an explosive charge, comprising a container having at least one open end, an explosive charge including a primer chargesensitive to flame ignition in said container, and means for retaining said primer charge within said container without seriously impairin the eli bility of the primer charge said means consls mg 0 a t in for] closing the open end of said container and a recess between said primer charge and said foil, said recess facilitating the rupture of said foil for ignition of said primer charge.

2. An ignitor according to claim 1, wherein said recess is formed by a cavity impressed into the surface of said primer charge.

3. An ignitor according to claim 2, wherein said cavity has the configuration of a portion of a sphere.

4. An ignitor according to claim 1,'wherein said foil is spaced from the surface of said primer charge, whereby said recess is formed.

5. An ignitor according to claim 2, wherein said foil is spaced from the surface of said p'rimer charge.

6. An ignitor according to claim 1, wherein said container means is provided with external screw thread means.

7. An ignitor according to claim 2, wherein said container means is provided with external screw thread means.

8. An ignitor according to claim 1, wherein said explosive chargeincludes at least two discrete zones of explosive materials of different classes.

9. An ignitor according to claim 8, wherein said explosive charge includes charge, initiating charge means and sustaining charge means.

10. An ignitor according to claim l, wherein said foil is aluminum. 

2. An ignitor according to claim 1, wherein said recess is formed by a cavity impressed into the surface of said primer charge.
 3. An ignitor according to claim 2, wherein said cavity has the configuration of a portion of a sphere.
 4. An ignitor according to claim 1, wherein said foil is spaced from the surface of said primer charge, whereby said recess is formed.
 5. An ignitor according to claim 2, wherein said foil is spaced from the surface of said primer charge.
 6. An ignitor according to claim 1, wherein said container means is provided with external screw thread means.
 7. An ignitor according to claim 2, wherein said container means is provided with external screw thread means.
 8. An ignitor according to claim 1, wherein said explosive charge includes at least two discrete zones of explosive materials of different classes.
 9. An ignitor according to claim 8, wherein said explosive charge includes charge, initiating charge means and sustaining charge means.
 10. An ignitor according to claim 1, wherein said foil is aluminum. 